Melanoma cells produce multiple laminin isoforms and strongly migrate on α5 laminin(s) via several integrin receptors

Melanoma cells express and interact with laminins (LMs) and other basement membrane components during invasion and metastasis. In the present study we have investigated the production and migration-promoting activity of laminin isoforms in melanoma. Immunohistochemistry of melanoma specimens and immunoprecipitation/western blotting of melanoma cell lines indicated expression of laminin-111/121, laminin-211, laminin-411/421, and laminin-511/521. Laminin-332 was not detected. In functional assays, laminin-111, laminin-332, and laminin-511, but not laminin-211 and laminin-411, strongly promoted haptotactic cell migration either constitutively or following stimulation with insulin-like growth factors. Both placenta and recombinant laminin-511 preparations were highly active, and the isolated recombinant IVa domain of LM alpha 5 also promoted cell migration. Function-blocking antibodies in cell migration assays revealed alpha 6 beta 1 integrin as the major receptor for laminin-111, and both alpha 3 beta 1 and alpha 6 beta 1 integrins for laminin-332 and laminin-511. In contrast, isolated LM alpha 5 IVa domain-promoted melanoma cell migration was largely mediated via alpha V beta 3 integrin and inhibited by RGD peptides. Given the ubiquitous expression of alpha 5 laminins in melanoma cells and in melanoma-target tissues/anatomical structures, as well as the strong migration-promoting activity of these laminin isoforms, the alpha 5 laminins emerge as putative primary extracellular matrix mediators of melanoma invasion and metastasis via alpha 3 beta 1 and other integrin receptors. (C) 2010 Elsevier Inc. All rights reserved.